Calculate how much soil you need for raised beds, gardens, and landscaping projects. Get volume in cubic yards and bags needed.
Soil Calculation Formulas
Rectangular Bed
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Circular Bed
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Bags Needed
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Weight Estimate
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Bed Shape
Soil Type
Recommended Depths
Soil Needed
Cubic Yards-
Cubic Feet-
1 cu ft Bags-
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40 lb Bags-
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Cost (Bulk)-
With 20% Settling-
Calculating Soil for Your Garden
Whether you're filling raised beds, starting a new garden, or improving existing soil, knowing exactly how much you need saves money and trips to the store. Our soil calculator helps you determine the precise amount of topsoil, garden soil, potting mix, or compost for any project.
Soil is heavy and expensive to transport, so accurate calculations are essential. Running short means delays and additional delivery fees; over-ordering wastes money and leaves you with piles of excess soil.
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Multiple Shapes
Calculate for rectangular, circular, and triangular beds.
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Soil Types
Different weight calculations for topsoil, garden soil, and mixes.
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Cost Comparison
Compare bagged vs. bulk pricing for best value.
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Weight Estimates
Know how much your soil will weigh for transport planning.
Types of Soil and Their Uses
Different projects require different soil types. Using the right soil ensures healthy plant growth and successful gardening outcomes.
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Topsoil
The top 4-8 inches of natural soil, containing organic matter and nutrients. Best for: filling large areas, lawn establishment, general landscaping. Not ideal for containers or raised beds without amendments.
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Garden Soil
Topsoil enriched with compost and organic matter. Designed for in-ground planting. Better drainage and nutrients than plain topsoil. Use for: garden beds, borders, tree planting holes.
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Raised Bed Mix
Specially formulated blend—typically 60% topsoil, 30% compost, 10% perlite or vermiculite. Lightweight, well-draining, nutrient-rich. Perfect for raised beds and elevated planters.
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Potting Mix
Lightweight, soilless mix of peat moss, perlite, vermiculite, and bark. Excellent drainage for containers. Not for in-ground planting—it's too light and dries out quickly in open beds.
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Compost
Decomposed organic matter—the ultimate soil amendment. Mix into existing soil to improve structure, drainage, and nutrients. Usually added at 2-4 inches and tilled in. Also works as mulch.
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Fill Dirt
Subsoil with no organic content. Used for leveling, filling holes, and creating grades. Not for planting—nothing grows well in fill dirt. Cover with topsoil for any planting areas.
Soil Depth Guidelines
Different plants have different root zone requirements. Providing adequate depth ensures healthy root development and productive plants.
Plant Type
Minimum Depth
Ideal Depth
Notes
Lawn/Grass
4"
6-8"
Over prepared subsoil
Annual flowers
6"
8-10"
Shallow roots
Herbs
6"
8-12"
Most herbs have shallow roots
Leafy vegetables
6"
8-12"
Lettuce, spinach, kale
Tomatoes, peppers
12"
18-24"
Deep root systems
Root vegetables
12"
18-24"
Carrots, potatoes, beets
Perennials
12"
18"
Varies by species
Shrubs
18"
24"
Native soil below OK
Trees
24"
36"
Width matters more than depth
Raised Bed Soil Guide
Raised beds are increasingly popular for vegetable gardening, and filling them correctly is crucial for success.
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Standard Raised Bed Formula
For a 4x8 ft bed at 12" deep: (4 × 8 × 1) ÷ 27 = 1.2 cubic yards. Add 20% for settling. Use raised bed mix or create your own: 60% topsoil + 30% compost + 10% perlite.
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Money-Saving Tip
For deep beds (18"+), fill the bottom third with logs, branches, straw, or cardboard (hugelkultur method). This reduces soil needed and creates long-term fertility as materials decompose.
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Settling Allowance
New soil settles 10-20% in the first year. Fill beds slightly higher than desired, or plan to add more soil after the first growing season.
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Annual Maintenance
Add 1-2 inches of compost annually to maintain soil level and fertility. This replaces nutrients removed by harvesting and compensates for ongoing settling.
Bagged vs. Bulk Soil
The choice between bagged and bulk soil depends on project size, access, and budget.
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When to Buy Bags
Best for: small projects (under 1 cubic yard), container gardening, limited access areas, specific soil types. More expensive but convenient. A cubic yard equals about 27 one-cubic-foot bags.
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When to Buy Bulk
Much more economical for large projects (1+ cubic yards). Bulk soil costs $25-$60 per cubic yard vs. $7-$15 per cubic foot bagged. Requires delivery access and a place to dump.
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Cost Comparison Example
4x8 ft raised bed (12" deep) needs ~1.2 cubic yards. Bagged (32 bags @ $5): ~$160. Bulk (1.5 yards delivered): ~$75-$100. The savings grow with larger projects.
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Quality Considerations
Bulk soil quality varies widely. Ask about the source and composition. Visit the supplier if possible. Premium bagged mixes are often higher quality than budget bulk soil.
Soil Improvement Tips
Even the best soil benefits from ongoing improvement. Building healthy soil is a continuous process.
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Test Your Soil
Before adding amendments, get a soil test from your local extension office ($15-$30). Know your pH, nutrient levels, and organic matter content. This prevents over-amending and guides purchases.
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Improve Clay Soil
Add 2-4 inches of compost and work it in deeply. Gypsum helps break up clay. Avoid tilling when wet. Plant cover crops in off-seasons. Improvement takes 2-3 years of consistent effort.
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Improve Sandy Soil
Add compost generously—it increases water and nutrient retention. Mulch heavily to prevent moisture loss. Sandy soil improves faster than clay. Annual compost additions are key.
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Build Organic Matter
Healthy garden soil should contain 5-10% organic matter. Add compost, aged manure, leaf mold, or other organics. Mulch with organic materials that decompose into the soil.
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Common Mistakes
Don't add sand to clay (creates concrete-like soil). Don't use fresh manure near plants. Don't add lime without a soil test. Don't work soil when wet. Don't skip the compost.
Frequently Asked Questions
How much does a cubic yard of soil weigh?
It depends on the type: Topsoil weighs about 2,000-2,200 lbs per cubic yard. Garden soil is slightly lighter at 1,800-2,000 lbs. Potting mix is much lighter at 600-800 lbs. Wet soil can weigh 25-50% more than dry.
How many bags of soil fill a 4x8 raised bed?
At 12" deep: about 32 one-cubic-foot bags, 16 two-cubic-foot bags, or 1.2 cubic yards bulk. At 18" deep: about 48 one-cubic-foot bags or 1.8 cubic yards. Our calculator gives exact amounts for your dimensions.
Should I use garden soil or potting mix in raised beds?
Use a raised bed mix or garden soil blend—not potting mix alone. Potting mix is too light for raised beds (dries out quickly, blows away). Garden soil provides weight and nutrients. Mix potting elements (perlite) with garden soil for best results.
How do I fill a very deep raised bed affordably?
Use the hugelkultur method: fill the bottom 1/3 with logs, branches, leaves, straw, or cardboard. Top with cheaper fill soil or subsoil for the middle 1/3. Use quality garden soil for the top 12 inches where roots grow. This cuts costs 30-50%.
Can I use native soil in raised beds?
You can mix native soil with amendments if it's reasonably good quality. A 50/50 mix of native soil and compost works well. Don't use pure native soil—it often drains poorly in raised beds. Never use soil from unknown sources (may contain chemicals or diseases).
How much soil settling should I expect?
New soil typically settles 10-20% in the first year, more for loose mixes. Fill beds about 2 inches higher than desired to compensate. After the first year, annual settling is minimal—just top up with compost each spring.
What's the best soil mix for vegetables?
The classic raised bed mix: 60% topsoil, 30% compost, 10% perlite or coarse sand. Some gardeners prefer: 1/3 topsoil, 1/3 compost, 1/3 peat moss or coco coir. Both provide good drainage and nutrients. Add slow-release fertilizer at planting time.
How often should I replace raised bed soil?
You don't need to replace it—properly maintained soil lasts indefinitely. Add 1-2 inches of compost annually. Rotate crops to prevent nutrient depletion and disease. If soil becomes compacted or diseased, remove the top 6 inches and replace with fresh mix.
Examples
Filling a 10x8 raised bed 12 inches deep
A gardener is filling a new wooden raised bed that measures 10 ft long, 8 ft wide, and 12 in deep with topsoil for vegetables.
ResultApproximately 80 cubic feet, which is about 2.96 cubic yards (round up to 3 yd³).
Convert depth to feet: 12 in ÷ 12 = 1 ft. Volume in cubic feet is 10 × 8 × 1 = 80 ft³. Divide by 27 to get cubic yards: 80 ÷ 27 ≈ 2.96 yd³, which rounds up to 3 yd³ when ordering bulk. At a topsoil density near 76 lb/ft³, the load weighs roughly 80 × 76 = 6,080 lb, or about 3 short tons. Add a 10–20% buffer for settling so the bed stays full after the first watering.
Frequently asked questions
How do I decide between cubic yards (bulk) and bags?
One cubic yard equals 27 cubic feet, so it fills roughly 27 one-cubic-foot bags or 13–14 two-cubic-foot bags. As a rough cutoff, projects under 1 cubic yard are usually cheaper and easier in bags, while anything 1 yard or larger is far cheaper delivered in bulk. Bulk also avoids dozens of plastic bags but requires a place to dump the pile and a wheelbarrow to move it.
How deep should the soil be for vegetables versus a lawn?
Vegetables need much deeper soil than turf. Lawns thrive on 4–6 inches of topsoil over prepared subsoil, since grass roots stay shallow. Shallow-rooted vegetables like lettuce, herbs, and radishes do well in 6–8 inches. Tomatoes, peppers, and root crops want 12–18 inches, and serious deep-rooted crops like parsnips or potatoes prefer 18–24 inches. Building beds to the deeper number once is easier than topping them up every year.
What is the difference between topsoil, garden mix, and compost?
Topsoil is the upper layer of native mineral soil with some organic matter, sold as a general-purpose fill for lawns and grading. Garden mix (or raised-bed mix) is topsoil blended with compost and often perlite or vermiculite, designed to drain well and hold nutrients for planting. Pure compost is decomposed organic matter — too rich and too loose to use alone, but ideal as an amendment mixed into the top few inches of existing soil or as a yearly top-dressing.
How do I calculate soil for a raised bed step by step?
Measure inside length, inside width, and target fill depth, all in the same unit. Multiply L × W × D in feet to get cubic feet, then divide by 27 to get cubic yards. For example, a 10 ft × 8 ft bed filled 12 inches (1 ft) deep is 10 × 8 × 1 = 80 ft³, or about 3 cubic yards. Add 10–20% for settling, and subtract the volume of any hugelkultur logs or fill material you place at the bottom.
Do I need a drainage layer of gravel at the bottom of a raised bed?
For most raised beds sitting on open ground, no — a gravel layer can actually create a perched water table that keeps roots wetter, not drier. Instead, loosen the native soil below the bed and use a well-draining garden mix on top. Drainage layers are only useful for raised beds on solid surfaces (patios, decks, or rooftops), where excess water has nowhere to escape. In those cases use coarse gravel or expanded clay topped with landscape fabric, then the soil mix.
How much does a cubic yard of topsoil weigh?
Dry topsoil density is roughly 76 lb/ft³, so a cubic yard (27 ft³) weighs about 2,050 lb, or just over one short ton. Wet topsoil and dense fill dirt can run 2,400–2,800 lb per cubic yard. Check your truck or trailer rating before hauling — a half-ton pickup should not carry a full cubic yard of wet soil in a single trip.
Should I include a buffer for settling and waste?
Yes. Loose-fill soils and mixes high in organic matter settle 10–20% in the first season as the structure compacts and microbes break down organics. Order roughly 15% extra, or plan to top up with an inch or two of compost the following spring. A small buffer also covers shoveling losses and the inevitable wheelbarrow spills.
Sources
Web Soil Survey · USDA Natural Resources Conservation Service
